Effect of AlF3 seed concentrations and calcination temperatures on the crystal growth of hexagonally shaped α-alumina powders

Abstract To synthesize micro-sized and high crystalline α-alumina particles with uniformly and rapidly at low temperatures, various concentrated AlF 3 seeds were added into an anhydrous ethanol solution saturated by an aluminum hydroxide starting material, gibbsite Al(OH) 3 . Hexagonal shaped α-alumina powders highly crystallized were observed at lower temperature of 750 °C, in the ranges from 0.01–5.0 mol% seed concentrations, and the α-alumina crystal growth depends on the concentrations of added AlF 3 seed. When 1.0 mol% AlF 3 seeds were added, the largest α-alumina hexagonal crystals (average size about 4.8 m after calcination at 900 °C) were produced. Additionally the crystallinity and size of α-alumina particle increases linearly with the calcination temperature. The size rapidly increased with an increase of calcination temperatures to 800 °C and then gradually increased up to 900 °C. This result shows that crystal growth of α-alumina is affected by seed concentrations and crystallized calcination temperature.